Phase Transitions and Magnetic Monopole Production in the Very Early Universe

In grand unified models, the abundance of superheavy magnetic monopoles in the universe can be suppressed if (1) the phase transition which creates the monopoles occurs after much supercooling; and (2) immediately after the phase transition, the effective monopole mass is large compared with the temperature. These requirements impose constraints on the history of the early universe. The Georgi-Glashow SU(5) group probably breaks to SU(4) ⊗ U(1) before it reaches SU(3) ⊗ SU(2) ⊗ U(1).